Gas turbine engines include fuel injectors that are used to sustain turbine operation under a variety of operating conditions. In relatively small turbine engines of the type utilized in airborne environments, fuel flows at high altitudes are frequently quite low. This produces a fuel atomization problem inasmuch as typical swirl pressure atomizing start fuel injectors will not spray at the very low fuel flows, e.g., less than three pounds per hour, that are required at high altitudes on the order of 50,000 feet. In high altitude ignition in gas turbine engines, combustor volume must also be maximized, i.e., made available for combustion, to provide sufficient time for reaction. Moreover, the high fuel viscosity encountered in cold high altitude conditions adds further difficulty to achieving reliable operation.
Additionally, while ignition can be attained relatively easily at low speed conditions on the order of no more than ten percent of maximum engine speed, kinetic loading increases significantly with engine acceleration. Under such conditions, blowout may occur, particularly at higher speeds, so it is most important to avoid local overfueling of the typical start injector of the swirl pressure atomizing type as the resulting fuel maldistribution renders kinetic loading, i.e., difficulty in combustion or burning, an even more significant problem. Additionally, it is most important for the main fuel injectors to provide exceptionally good fuel atomization even at low speeds so that fuel evaporation problems do not further compound operational difficulties.
The present invention is directed to overcoming one or more of the above problems.